Fixed overlapping fragments issue.

Fast consercutive calls to #showFragment can have undesirable effects because
fragment manager doesn't handle transactions sychronously. This CL resolves one
of the scanrios where voicemail fetch status was calling #showFragment nearly
simulataniously to the #onHandleIntent call.

This issue may show itself again and I'm looking into more long term solutions
but we should be fine in the short term since the all of our fragment logic
is implemented.

Bug: 74051208,74621909
Test: manual
PiperOrigin-RevId: 188956984
Change-Id: I0796e31b03e0b749ae7e81f82859ea6f814a5fb5